I should have mentioned for me personally, I add meringue powder...but that makes the icing crust...something you don't want. And 1 cup of icing sugar just to make the flour icing a bit stiffer. But as I said, personal preference.
You could try cooked flour frosting. Traditionally made with all butter, but you can substitute all shortening. I have, and it works well. Pipes great...I've made designs, although not piped flowers. But I'm sure you could. Here's the recipe I use. Follow exactly and you can't go wrong.
Even Better (!) Cooked Flour Frosting (with flavor variations & Vegan ...
I tried water and tylose and I found it became to gummy. So I went back to alcohol. With the alcohol, it lasts a long time. Alcohol also keeps it sterile so mould won't grow. Made with water, you would have to refrigerate.
There are two ways wmartz.
1. Take a small bottle with a tight fitting lid. Fill bottle 3/4 full with clear alcohol, rum, vodka. Add about a heaping tablespoon of ready made or homemade gumpaste. Shake bottle well. Let sit overnight. The gumpaste will break down. It should be soupy, not too thick. If it's too thick, just a touch more alcohol.
2. Same as above except add 2 heaping tsp of tylose powder to the alcohol and shake. You won't have to wait overnight to use....